Recently, it is very important to reduce the weight of mobile terminals, such as portable computers, PDA and hand-held phones, in order to make it possible to effectively and easily carry them. The main part contributing to the weight of a mobile terminal is a battery to supply power to the terminal. Further, the less that a power consumption of a semiconductor memory chip used in the mobile terminal (hereinafter, referred to as “mobile memory chip”) can be reduced, the more the capacity of the battery needs to be increased. Accordingly, the weight of the mobile terminal can be reduced by lowering power consumption of the semiconductor memory chip, and therefore additional research regarding power consumption of the mobile memory chip is still required to improve the mobile terminals.
Meanwhile, as mobile terminals develop into multimedia devices to provide various services, high speed operation is required to process a huge amount of data. Accordingly, high data transmission rate in the mobile memory chip is essential to improved operating speed of the mobile terminals and improvement in the data transmission rate is a key issue of the study on mobile memory chip.
Recently, a low power DDR2 (hereinafter, referred to as “LPDDR2”) technique has been developed and this technique dramatically improves both the power consumption of the mobile terminals and the data transmission rate. The LPDDR2 technique can implement the data transmission rate of 800 Mbps, which is currently the highest in the industry, at a power supply voltage of 1.2V. Further, in the case where a method of manufacturing an ultra-fine line width of 66 nm is applied to the mobile memory chip, the mobile memory chip may have a package size of approximately 9 mm×12 mm.
In the LPDDR2 technique, a one-chip solution is provided. The function of the one chip solution is to provide various modifications of the data processing speed and operation modes in the mobile memory chip according to the operating environments of the mobile terminals in which the mobile memory chip is embedded.
As mentioned above, the LPDDR2 technique can reduce the power consumption dramatically and also increase the data transmission rate, and therefore the LPDDR2 technique has been widely used as an optimized memory device technique in the mobile terminal.
In the LPDDR2 technique, a mode register write operation, which writes mode register information in a plurality of registers, is prescribed in a specification; however, a mode register read operation, in which the mode register information is read out from the plurality of registers, is not prescribed in the specification.